Rapid free-form fabrication, commonly referred to as rapid prototyping, is an additive process often used to produce three dimensional objects, such as gas turbine engine component models. A useful rapid prototyping process is known as stereolithography. In general, stereolithography refers to a method of rapidly building up an object in a layer by layer fashion. In this process, an ultraviolet laser beam selectively scans a portion of a bath of photocurable liquid resin to produce a predetermined pattern. Upon contact with the laser beam, the resin rapidly polymerizes (solidifies). This process enables rapid and accurate fabrication of three dimensional objects which would otherwise be produced by lengthy molding and machining processes.
Solid or hollow three dimensional objects may be produced by stereolithography. For example, QuickCast.TM. by 3D Systems, Inc. may be used to produce investment casting patterns with a honeycomb-like internal structure. This build style facilitates drainage of uncured resin from within the internal cavities of the pattern. The internal voids in the pattern permit the pattern to collapse upon itself as it expands against a mold during investment casting processing, as opposed to exerting excessive force against the mold walls and causing cracking.
Although stereolithographically produced objects are useful, their direct use is limited by the physical properties inherent in the resins suitable for stereolithography processing. Resins suitable for this type of processing are photocurable liquids and objects produced with such resins often experience creep effects or long term dimensional instability. Thus, although these objects have great use as investment castings patterns or as non-functional prototypes, their use in other applications such as tooling fixtures is limited.
Conventional tooling fixtures are usually metal which makes them both costly and difficult to form. In addition, the design of tooling fixtures is dependent upon component size and shape. Thus, the part specific nature and the complexity of tooling fixtures makes them both time consuming and costly to manufacture. It is also not economical to manufacture these metallic tooling fixtures in small lots, which is often necessary.
Accordingly, there exists a need for a strong, dimensionally stable object, especially a tooling fixture, as well as a method for producing such an object.